Today there are many large and old riveted structures, such as transportation bridges and materials-handling systems, including ore and coal bridges and unloaders, that are still subjected to regular cyclic service. Some of the structures are carrying loads greater than those considered in the original design calculations. Many of these structures were designed within the framework of criteria that either neglected the effects of cyclic loading or were based on early limited notions of structural fatigue. The generally accepted method of repair or rehabilitation for riveted structures has been to replace entire members that either contain fatigue cracks or are suspected to be overstressed in cyclic loading (i.e., to have accumulated fatigue damage). However, the recognition that high-strength bolted connections will develop, approximately, the fatigue strength of the base or connected material led to the proposal that existing riveted ore bridge connections "be protected" by replacing rivets with high-strength bolts. The program described herein was conducted by Bethlehem Steel Corporation to study the effectiveness of structural rehabilitation by the replacement of rivets in critical locations with high-strength bolts as a more economical alternative to the replacement of entire members. A riveted truss chord to panel point connection typical of ore bridges was selected as the test vehicle because of the available documentation of operation and maintenance of such in-house structures. Full-scale models of the prototype connection were fatigue-tested under constant load amplitude to quantify the life extension resulting from rehabilitation of damaged members. The fatigue life was found to be increased two to six times. Variable amplitude tests simulating the service spectrum of the prototype and constant amplitude tests of actual connections removed from the prototype structure confirmed the effectiveness of the rehabilitation technique.
"Fatigue Life Extension of Riveted Connections," Journal of the Structural Division, Proceedings of the American Society of Civil Engineers, v. 101, ST12, December 1975, pp 2591-2608. Discussion and Closure, Journal of the Structural Division, Proceedings of the American Society of Civil Engineers, v. 103, ST7, July 1977, pp 1495-1496.